1. Field of Invention
The present invention relates generally to storage area networks (SANs), and more particularly to having SAN devices log data to a reserved area on a storage unit in the SAN.
2. Description of the Related Art
As computing power and storage requirements increased, a problem developed relating to properly and cost effectively matching storage and computing resources. Directly connecting the storage units of the computing hosts often resulted in excess storage capacity to ensure that at least enough was present. This was not cost effective. To address this problem storage area networks (SANs) were developed. In a SAN a series of hosts are connected to a series of storage units using a switching network, the switching network being called a fabric. By this architecture storage capacity could be dynamically added and allocated to the hosts.
The fabric is developed using a series of interconnected switches. Properly connecting the switches allows high performance connections between the hosts and the storage unit.
One further requirement of modern computer systems is high reliability, particularly for the hosts, storage units and switches in a SAN, as loss of services of the units could result in large downtime costs or delay in providing the related services. Thus, it is desirable that error logs be kept of each device to aid troubleshooting efforts. But this is complicated in the switches of a SAN because the switches have only very limited long term storage capabilities.
While it was stated above that properly connecting the switches allows high performance, as the SAN grows determining the proper connections becomes extremely difficult. Modern switches include performance monitoring capabilities, but again limited storage capacity has limited the use that can be made of any performance monitoring data.
The configuration of the SAN is further complicated by security features. In many cases it is desirable that certain hosts not be able to have access to certain storage units, or even just areas of storage units. This is accomplished with various zoning techniques, such as those shown in U.S. patent applications Ser. No. 09/426,567 “Method And System For Creating And Implementing Zones Within A Fibre Channel System,” by David Banks, Kumar Malavalli, Paul Ramsay, Kha Sin Teow, and Jieming Zhu, filed Oct. 22, 1999 and Ser. No. 10/123,996 “Fibre Channel Zoning By Device Name In Hardware” by Ding-Long Wu, David C. Banks and Jieming Zhu, filed Apr. 17, 2002, which are hereby incorporated by reference. Zoning works by establishing tables of devices allowed to communicate. But these tables can get very large in complicated and/or large networks and the storage capacity of the switches is small. While the second application discloses using a virtual system with a larger table maintained in memory to supplement smaller tables maintained in the hardware, the tables still have a limited size.
It would be desirable to increase the data storage capacity of switches to allow larger tables and to allow much more storage of error or diagnostic data and performance monitoring data for all devices in the SAN to allow better diagnosis and management of the SAN.